Electric contact grease

ABSTRACT

AN IMPROVED CONTACT GREASE IS PROVIDED. THE GREASE CONSITS ESSENTIALLY OF (A) A MAJOR AMOUNT OF PARAFFINIC MINERAL OIL; (B) 10 TO 20 PERCENT BY WEIGHT OF, AS A THICKENING AGENT, A MIXTURE OF METALLIC SOAPS, SAID MIXTURE OF METALLIC SOAPS CONSISTS ESSENTIALLY OF (I) 40 TO 65 PERCENT BY WEIGHT OF BARIUM SOAP; (II) 25 TO 40 PERCENT BY WEIGHT OF LITHIUM SOAP AND (III) 10 TO 20 PERCENT BY WEIGHT OF ALUMINUM SOAP; AND (C) 7 TO 15 PERCENT BY WEIGHT OF AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF TRICHLORODIPHENYL, TETRACHLORODIPHENYL, PENTACHLORODIPHENYL, HEXACHLORODIPHENYL, POLYCHLOROTRIPHENYL, PENTACHLORODIPHENYL OXIDE, PENTRACHLOROPHENYL BENZOATE, HEXACHLORODIPHENYL METHANE, AND PENTACHLORODIPHENYL KETONE.

United States Patent US. Cl. 25233.3 4 Claims ABSTRACT OF THE DISCLOSURE An improved contact grease is provided. The grease consists essentially of (a) a major amount of parafiinic mineral oil;

(b) to 20 percent by weight of, as a thickening agent, a mixture of metallic soaps, said mixture of metallic soaps consists essentially of (i) 40 to 65 percent by weight of barium soap;

(ii) 25 to 40 percent by weight of lithium soap and (iii) 10 to 20 percent by weight of aluminum soap;

and

(c) 7 to percent by weight of at least one member selected from the group consisting'of trichlorodiphenyl, tetrachlorodiphenyl, pentachlorodiphenyl, hexachlorodiphenyl, polychlorotriphenyl, pentachlorodiphenyl oxide, pentachlorophenyl benzoate, hexachlorodiphenyl methane, and pentachlorodiphenyl ketone.

The present invention relates to an electric contact grease which has particular application in power switches of electrical machines and apparatuses.

Usual electric contacts of, for example, television and radio are subjected to contact failure and contact welding and are responsible for troubles such as sound noise, picture failure, impossibility of contact opening and the like.

These troubles are prevented to some extent by using existing electric contact greases. However, such use has not been completely satisfactory due to the complicated nature of the phenomenon of the electric contact. Contact failures are usually caused by oxidation, sulfation, and wear of contact metal surfaces and sludge formed by oxidation, polymerization, and burning of the grease itself.

Excellent contact greases to remove such troubles have been long desired especially in the case of base metal contact such as copper or brass which are easily subjected to cont-act failures.

Therefore the role of contact grease is to prevent oxidation, sulfation and wear of contact metals and thereby to stabilize the electric contact resistance and to prevent noise and at the same time, prevent contact welding by restraining temperature rise of the electric contacts.

An object of the present invention is to provide a contact grease capable of suppressing a rise in the electric contact resistance of an electric contact.

A further object of the present invention is to provide a contact grease which prevents an electric contact from wearing.

Another object of the present invention is to provide a contact grease useful for use in an electric contact formed by copper, brass, phosphorous bronze, beryllium copper and nickel silver.

These and other objects of the present invention will be apparent upon consideration of the following detailed description.

A contact grease according to the present invention consists essentially of a major amount of paraflinic mineral 3,632,509 Patented Jan. 4, 1972 oil, 10 to 20 percent by weight of, as a thickening agent, a mixture of metallic soaps and 7 to 15 percent by weight of at least one member selected from the group consisting of chlorinated aromatic hydrocarbon and its derivatives. Said mixture of metallic soaps consists essentially of 40 to 65 percent by weight of barium soap, 25 to 40 percent by weight of lithium soap and 10 to 20 percent by weight of aluminum soap in accordance with the present invention. The novel contact grease according to the present invention prevents an electric contact from failing, and welding which ensures a satisfactory contacting action for a longer time period especially when applied to an electric contact made of corrodible metal such as copper, brass, phosphorous bronze, beryllium copper and nickel silver. Antirust agent and/or antioxidant are preferably added to the composition of the grease.

A contact grease according to the present invention can employ chlorinated aromatic hydrocarbon or its derivatives having a boiling point higher than 300 C. Chlorinated aromatic hydrocarbon or its derivatives serve to prevent temperature rise and contact wear by restraining burning of grease by arcing and at the same time by acting as lubricating agent. A better result can be obtained by employing at least one member selected from the group consisting of trichlorodiphenyl, tetrachlorodiphenyl, pentachlorodiphenyl, hexachlorodiphenyl, polychlorotriphenyl, pentachlorodiphenyl oxide, pentachlorophenyl benzoate, hexachlorodiphenyl methane, and pentachlorodiphenyl ketone. Among those members, trichlorodiphenyl, tetrachlorodiphenyl, hexachlorodiphenyl, polychlorotriphenyl achieve the best results in accordance with the present invention.

If the chlorinated aromatic hydrocarbon or derivative thereof is present in an amount lower than about 7% by weight, the temperature rise of contact goes higher, while an amount greater than about 15% by weight makes it difficult to produce a contact grease having a good homogeneity.

The paraffinic mineral oil defined herein includes pure paraffinic mineral oil as well as impure paraflinic mineral oil having incorporated therein a small amount, for example up to 30% by weight of aromatic and/or naphthenic mineral oil. It is preferable that the paraffinic mineral oil has a viscosity of 40 to 180 cst. (at 37.8 C.) and an aniline point higher than in the ASTM D6ll-55T (American Society for Testing Materials).

One can employ barium soap, lithium soap and aluminum soap including those containing an aliphatic fatty acid radical. Their chemical formulae are expressed by B-a(RCO O) Li(RCOO) and Al(RCOO) respectively wherein R is an alkyl radical. However, these chemical formulae should not be construed to define only pure substances, but include impure substances incorporated with unavoidable impurities. For example, Al(RCOO) commercially available includes Al(OH) (RCOO) in an amount of less than 20 percent by weight and is operable for production of a contact grease according to the present invention. It is preferable that the R in the chemical formulae contains 12 to 20 carbon atoms. The most preferable barium soap, lithium soap and aluminum soap is one which includes a stearic acid radical.

The content of free fatty acid of these metallic soaps is desirably small, preferably lower than 2 percent by weight.

In connection with the weight percent of the mixture of metallic soaps, the following is noted: The barium soap in an amount higher than 65 percent by weight increases the electric contact resistance and the barium soap in an amount lower than 40 percent by weight impairs the resistance to welding of electric contact; the lithium soap in an amount lower than 25 percent by weight increases the electric contact resistance and the lithium soap in an amount higher than 40 percent by weight impairs the resistance to the welding; and the aluminum soap in an amount higher than 20' percent by weight produces a contact grease which has a low pour point and is inferior in the resistance to heat and the aluminum soap in an amount lower than 10 percent by weight results in a contact grease which is poor in homogeneity.

When the amount of the mixture of the metallic soaps in the grease is less than about 10 percent by weight, the resultant contact grease is too soft to hold its shape as it is. On the other hand, an amount of the mixture higher than about 20 percent by weight results in a contact grease which is too hard.

A contact grease according to the present invention can be improved by using an antioxidant and/ or a rust inhibitor. The preferable antioxidants are n-butyl-p-aminophenol, di-sec-butyl-p-phenylenediamine, 4,4'-tetramethyl-diaminodiphenyl methane, oc-naphthylamine, n,n'-di-salicylidene-1,2propylenediamine, 2,6-di-tert-butyl phenol, 2,4-dimethyl-6-tert-butyl phenol, 2,6-di-tert-butyl-p-cresol,

4,4-methylenebis (2,6-di-tert-butyl phenol), 2,2-methy1enebis (4-methyl-6-tert-butyl phenol) 4,4-butylidene bis(3-n1ethyl-6-tert-butyl phenol).

The preferable rust inhibitor is sonbitan mono-oleate, salt of dinonyl naphthalene sulphonate, a-(2-carboxy phenoxy) stearic acid. The amount of the antioxidant is preferably 0.01 to about 3 percent by weight, that is 0.01 to 3 percent by weight of the antioxidant and about 97 to 99.99 percent by weight of the contact grease. The amount of the rust inhibitor is 0.01 to about 4 percent by weight of the rust inhibitor and about 96 to 99.99 percent by weight of the contact grease.

A mixture of the paraflinic mineral oil, the mixture of the metallic soaps, the chlorinated aromatic hydrocarbon or its derivatives with or without antioxidant and rust inhibitor is heated at 200-250 C., to make a homogeneous liquid and then cooled to room temperature. The cooled mixture is milled by a usual method, e.g. employing three roll mills, and is subjected to the removal of airfoams at a reduced pressure.

The resulting greases are smooth and buttery in texture and have excellent mechanical and thermal stability.

The invention is illustrated in the ensuing examples which are for the purpose of illustration and are not considered to be wholly definitive with respect to scope or conditions. In the examples g. represents grams.

EXAMPLE 1 A mixture of 74.7 g. of paraflinic mineral oil having viscosity of 60 cst. at 37.8 C. and aniline point of 11.7 C., 8 g. of barium stearate (M.P. 235 C.), 5 g. of lithium stearate (M.P. 221 C.), 2 g. of aluminum stearate (M.P. 112 C.), g. of polychlorotriphenyl, 0.1 g. of 4,4- tetramethyl diamino diphenyl methane and 0.2 g. of sorbitan monooleate is stirred and heated at 230 to 240 C.

After being homogenized the mixture is poured into a dish and cooled to room temperature, milled with a three roll mill, and then the remaining foam of the grease is removed under reduced pressure. The resulting grease is stable and has an ASTM penetration of 332 and a pour point of 120 C. The grease is applied to an electric con tact made of copper and brass. The grease action is shown in Example No. l of the table.

EXAMPLE 2 A mixture of 70.5 g. of paraflinic mineral oil having viscosity of about 50 cst. at 37.8 C. and aniline point of 1 02.7 C., 10 g. of barium stearate (M.P. 235 C.), 7 g. of lithium stearate, 4 g. of aluminum stearate, 8 g. of polychlorotriphenyl, and 0.5 g. of 2,6-di-tert-butyl phenol is heated at 235 to 245 C. After being homogenized the mixture is cooled, milled and treated in a manner similar to that of Example 1. The testing result carried out similarly to Example 1 is shown in the table.

EXAMPLE 3 A mixture of 73.8 g. of parafiinic mineral oil having viscosity of 120cst. at 37.8 C. and aniline point of 114.9 C., 6 g. of barium stearate (M.P. 250 C.), 4 g. of lithium stearate (M.P. 221 C.), 2 g. of aluminum stearate, 14 g. of polychlorotriphenyl, 0.2 g. of Na salt of dinonyl naphthalene sulphonate is stirred and heated at about 250 C. The clear fluid solution is treated in a way similar to that of Example 1. The testing result carried out similarly to Example 1 is shown in the table.

EXAMPLE 4 A mixture of 75.4 g. of parafi'inic mineral oil having viscosity of cst. at 37.8 C. and aniline point of 114.0 C., 7 g. of barium stearate, 5 g. of lithium laurate (M.P. 219 C.). 1.5 g. of aluminum stearate, 8 g. of hexachloro diphenyl, 0.1 g. of tetra base and 3 g. of sorbitan monooleate is heated in a beaker until its temperature reaches about 240 C. The resulting mixture is treated in a way similar to that of Example 1. The testing result carried out similarly to Example 1 is shown in the table.

EXAMPLE 5 A mixture of 72.9 g. of parafiinic mineral oil having viscosity of 60 cst. at 37.8 C. and aniline point of 111.7 C., 10 g. of barium stearate, 5 g. of lithium laurate (M.P. 219 C.), 3 g. of aluminum stearate and 9.1 g. of tetrachloro diphenyl is stirred and heated in a beaker until its temperature reached about 250 C. The resulting mixture is treated in a way similar to that of Example 1. The testing result carried out similarly to Example 1 is shown in the table.

EXAMPLE 6 A mixture of 70.9 g. of paraflinic mineral oil having viscosity of 80 cst. at 37.8 C. and aniline point of 114.0 C., 9 g. of barium stearate (M.P. 240 C.), 6 g. of lithium laurate (M.P. 219 C.), 2 g. of aluminum stearate (M.P. C.), 12 g. of polychlorotriphenyl and 0.1 g. of tetra base is stirred and heated in a beaker and treated in a way similar to that of Example 1. The testing result carried out similarly to Example 1 is shown in the table.

EXAMPLE 7 EXAMPLE 8 A mixture of 73.7 g. of parafiinic mineral oil having viscosity of 80 cst. at 37.8 C. and aniline point of 114.0 C., 8 g. of barium stearate, 6 g. of lithium stearate, 2.2 g. of aluminum stearate, 10 g. of polychlorotriphenyl and 0.1 g. of tetra base is stirred and heated in a beaker and treated in a way similar to that of Example 1. The testing result carried out similarly to Example 1 is shown in the table.

EXAMPLE 9 A mixture of 76.5 g. of parafiinic mineral oil having viscosity of cst. at 37.8 C. and aniline point of 114.9 C., 8 g. of barium stearate, 4 g. of lithium stearate, 1.5 g. of aluminum stearate, 9 g. of hexachloro diphenyl, and 1.0 g. of 2,2-methylene bis(4-methyl-6-tert-butyl phenol) is stirred and heated in a beaker and treated in a way similarly to that of Example 1. The testing result carried out similarly to Example 1 is shown in the table. 

